The transfer apparatus may be an intermediate stage between storage facilities and a processing machine or, as in the case of containers or cassettes filled with long stock, a station for individually unloading pieces of long stock before they are moved to a processing machine.
While the following description of the invention will be restricted to describing its application in connection with a sawing machines, it will be understood that such restriction is not intended thus to limit the possible uses of the invention, but that the invention may be practiced with no less efficiency and effect with any kind of processing machine to which long stock is fed by a conveyor. "Long stock" as used herein is intended to be any article having one dimension which exceeds its other two dimensions.
The conveyor referred to above typically is a roller track and serves to feed long stock to the cutting machine for processing therein and for removing the stock from the cutting machine after a processing. The defined orientation of the stock on the track may be attained by an appropriate symmetrical configuration of the roller track, such as, for instance, a V-shaped configuration, and by adapting the lay-out of the cutting machine to given operating conditions.
A crane or hoist having a load beam provided with laterally protruding booms or tines or the like is used to place bar-shaped workpieces on the roller tracks. By means thereof, long stock is transferred from a storage facility to the roller track, and unused or left-over material is transferred from the roller track to the storage facility. In a known arrangement, the roller track or at least that portion of it which is located immediately adjacent the cutting machine is for this reason arranged substantially parallel to the long stock in the storage facility so that the stock in being transferred from its storage position to onto the roller track needs only to be moved vertically and horizontally.
In the context of the present invention the storage facility is composed of cages or shelves arranged in storage racks aligned laterally of the longitudinal dimension of the long stock. For the purpose of transferring long stock to and from the shelves, the hoist may be moved towards them across the aisle between the storage racks.
To avoid lost time in the operation of the hoist and an inefficient use of the main operating time of the cutting machine, a transfer apparatus is provided which is similar to the one disclosed by U.S. Pat. No. 4,881,634--Stolzer, issued Nov. 21, 1989, and incorporated by reference herein. In the known apparatus material next in line to be processed may be kept in a state of abeyance or readiness, once processing of a preceding lot has been completed, to allow removal of the previously processed material and its replacement by the material next to be processed, before returning possible remainders of the processed material to the storage facility. The processing time of a given lot allows for sufficient time for the hoist to move remainders of previously processed material to a storage facility and to bring by material next to be processed.
In the prior art apparatus, movement of the hoist and its load beam, of any materials transfer means, as well as of the roller track, is automatically controlled numerically to the extent possible by the lay-out of the storage facility, the positioning or orientation and kind of long stock, etc. Since these aspects are well known to persons skilled in the art of materials handling, they will not be explained in detail again. Persons skilled in the art will, however, appreciate, that those aspects or principles are equally applicable to the present invention. Therefore, in explaining the invention, general knowledge will be assumed of the fact that the operation of the apparatus is controlled automatically and that, therefore, a detailed description of the controls per se may be dispensed with.
The known apparatus utilizes a roller track mounted on a support frame and guide ways or tracks continuing laterally upwardly from the fame. Support elements for the long stock may be moved along the tracks. The upper position which may thus be reached by the support elements serves to load or retrieve long stock by the hoist. The lower position corresponds to a transfer position between long stock and roller track. The operating sequence is such that one of the support elements supporting the lot next in line to be processed has moved downwardly so that the stock may be placed on the roller track preparatory to a processing operation, whereas the other support element and the processed stock thereon have moved to the upper position where the hoist may take over the processed stock. Following the depositing of the processed stock in the storage facility the hoist will return carrying with it stock to be processed next and place it into the retainer located in the upper position.
While such handling apparatus has proven to be satisfactory, it can still be improved. The V-shaped upwardly flaring guide tracks of the two support elements require relatively large space transversely of the long stock, particularly in view of the fact that in the region of the upper position of the support elements, the hoist requires some space for its movements. The two upper positions of the support elements are spaced relatively far from each other, so that for removing stock to be returned to storage and for depositing stock next to be processed, the hoist must be moved to different positions.
Each of the support elements, as well as the separate guide tracks in the known apparatus, have to be separately moved and controlled. This requires undue complexity in terms of controls and materials. For moving between their upper and lower positions each of the support elements requires its own lifting drive, and each of these requires its own controls. As has been stated above, each of the support elements requires its own guide track, which needs to be assembled and mounted on the support frame.
The known support elements are made of forks made up of prongs arranged consecutively in the direction of the longitudinal dimension of the long stock. The prongs need to be arranged so they may intermesh without colliding with the loading means of the hoist on the one hand, and with the spacing of the rollers of the roller track, on the other. The added space thus required in the direction of the longitudinal extent of the stock prevents the rollers from being spaced closely together. Such close spacing would, however, be desirable, especially in that section of the roller track which is adjacent to the cutting machine. The section close to the cutting machine may have to take up short left-over pieces of the long stock. These, of course, could only be conveyed without tilting if the rollers are spaced sufficiently closely together. However, such close roller spacing cannot be achieved because of the limitations set by the spatial requirements of the prongs of the support elements.
The distance between the upper positions of the support elements disadvantageously affects the operating time of the hoist; for in order to deposit stock next to be processed on the support element on one side and thereafter to retrieve processed stock from the support element on the other side for return to storage, the hoist, as set forth above, has to travel to the different upper positions of the supports.